Estimating the non-market benefits of water quality improvement for a case study in Spain: A contingent valuation approach

► Applying the contingent valuation method, we estimate the social benefits derived from improving water quality in the context of the European Water Framework Directive. ► We address the problem of zero and protest responses applying a Spike model and a sample selection bias model. ► The results show that the willingness-to-pay estimates are sufficiently robust to accurately inform decision-making and that sample-selection bias is not a problem.